488
FXUS63 KFGF 121737
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
1237 PM CDT Sun May 12 2024

.KEY MESSAGES...

- Smoke from Canadian wildfires will be present across the
  region throughout the day today.

- There is a chance for frost for areas north of US Highway 2
  tonight into Monday morning.

&&

.UPDATE...
Issued at 1237 PM CDT Sun May 12 2024

Near term trends are still in line with last update, with RH
values already around 25 percent even without reaching forecast
highs yet in parts of MN. Winds continue to gust as high as 30
mph over parts of the Red River Valley, but RH is remaining
higher. RAP/HRRR smoke models show the main periods of smoke
exiting the region to the south this evening, but patchy smoke
may still linger longer into the night if trapped by the
nocturnal inversion. Adjustments were made to reflect this into
the nighttime period during this update.

UPDATE
Issued at 1018 AM CDT Sun May 12 2024

Despite surface smoke, the smoke aloft so far has not been
opaque enough to limit incoming daytime radiational heating,
and mixing is better than originally anticipated. Td trends are
a bit lower, temps a bit higher, and gusts 20-27 mph have been
reported. Considering these trends I made some adjustments to
better reflect potential afternoon conditions. Result is RH
values likely in the 20-25% range with gusts continuing around
25 mph. Considering this, I issued an SPS for near critical fire
weather conditions based on previous partner coordination in
our MN counties.

UPDATE
Issued at 650 AM CDT Sun May 12 2024

There is uncertainty in the affect smoke will have on fire
weather conditions today. Very dry air mass moving into the area
along with gusty winds up to 30 mph are forecast today. Initial
thought was that smoke was going to hinder daytime mixing
potential, keeping fire weather conditions from developing by
limiting minimum relative humidity values and to an extend wind
gusts. However, looking at yesterday`s observations in this air
mass upstream in Saskatchewan showed that despite thick smoke
cover, RH values still dipped into the teens to low 20s percent.
Should this happen in our area today, near critical to critical
fire weather conditions will develop. There is around a 30-50%
for near critical fire weather conditions developing, along with
20% chance in critical fire weather conditions. Highest chance
for this to occur exists in northwest Minnesota.

&&

.DISCUSSION...
Issued at 410 AM CDT Sun May 12 2024

Synopsis:

A cold front is passing through our area this morning as
observed by surface observations. This cold front will be south
of our area by mid morning, with relatively cooler air pushing
into the region behind a passing upper low moving through MB and
ON. Smoke from Canadian wildfires will fill into the region
behind this front, lingering throughout the day today, possibly
into Monday. North Dakota and Minnesota will remain in the
subsident region south and behind the passing upper low,
followed by upper ridging Monday keeping conditions dry today
and Monday. Upper troughing aloft then extends into the Northern
Plains and Upper Midwest mid to late next week bringing one or
more rounds of showers and weak thunderstorms. The chance for
widespread hazardous weather during this mid to late next week
period.

Smoke from Canadian wildfires today:

Surface observations early this morning are revealing reduced
visibilities from smoke, signaling smoke at the surface behind
the passing cold front. Given continued weak cold air advection
behind the front, smoke is expected to remain near surface level
throughout the day today. High confidence in this is backed by
most if not all smoke allowing models depicting this as well.
Smoke may thin a little during the afternoon as highest
concentrations may advect away from the area closer to the
frontal passage, but still will be noticeable throughout the
day. Smoke may may also hinder daytime heating some keeping
temperatures in the 60s to low 70s.

Frost potential tonight into Monday morning:

Optimal radiational cooling conditions in a dry air mass
forecast to reside over lower Canada into the Northern Plains
and Upper Midwest will allow temperatures to dip into the 30s.
There is still some uncertainty in where lowest dewpoints will
reside come nightfall tonight, but dry air mass filtering in
from the north would keep best chance for driest air in northern
counties north of US Highway 2. This in turn would give highest
frost potential at these locations with temperatures cooling to
their dewpoints under light winds and clear skies. Even with
smoke expected to be present, smoke does not affect radiational
cooling efficiency. As of now, there is a 40% chance frost
develops for these locations, with other areas within Minnesota
liable to see frost as well.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1237 PM CDT Sun May 12 2024

MVFR to VFR conditions due to the wildfire smoke. Visibilities are
going to hard to predict as there are some patches of thicker smoke
moving through. Overall the visibilities should improve by the
evening and with the smoke moving out completely later tonight.
Winds will remain out of the north through tonight, but KDVL will
begin shifting to the east around 05z while the rest of the TAF
sites remain northerly.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.

&&

$$

UPDATE...CJ/DJR
DISCUSSION...CJ
AVIATION...MM/DJR